Field of the Invention
The invention relates to an optoelectronic unit, having a base plate which carries an optoelectronic component with at least one optically active zone, a lens body having at least one lens associated with the optically active zone, and a spacing device being an integral component of the lens body.
In the production of optoelectronic units or modules, the precise optical coupling of the optically active zone of the optoelectronic component (such as a laser diode) to some further optical element (such as a fiber-optical waveguide) is problematic, especially if a plurality of optically active zones (such as a diode array) are to be coupled.
Published European Patent Application 0 506 438 A1, corresponding to U.S. Pat. No. 5,260,587, discloses a unit with an optoelectronic component in the form of a so-called LED array with a plurality of light-emitting diodes spaced apart in a line as the optically active zones and with a lens carrier which carries a number of individual lenses (lens array) corresponding in number and spacing to the diodes. The assembly and adjustment of the known unit is comparatively complicated and expensive, because of the lack of adjusting devices on the unit itself.
For the sake of easier assembly, Published European Patent Application 0 421 118 A1 describes a carrier body for a glassed-in lens that is fixed relative to a body which carries a laser diode. To that end, one flat side of the carrier body, after being adjusted, can be soldered to metallized small glass blocks that are secured to both sides of the body which carries the laser diode.
German Published, Non-Prosecuted Patent Application DE 43 42 844 A1, corresponding to U.S. application Ser. No. 08/661,076, filed Jun. 10, 1996, discloses a carrier that jointly carries an optoelectronic component with a laser diode array, and lenses that have to be positioned and fixed individually. Additional, separate lenses can be inserted into indentations in the carrier and form a mechanical stop for the component.
An optoelectronic unit which is known from Published European Patent Application 0 529 947 A1 includes as its first part a base plate (termination plate) which has a solder-coated contact spot for at least one optoelectronic component with an optically active zone, and reference points in the form of first alignment indentations. A component placed on the contact spot is automatically exactly positioned relative to the contact spot and therefore to the alignment indentations, upon reflux of the solder, utilizing the surface tension of the solder. An optical fiber to be coupled extends in a groove of a second plate and ends at the end region toward the base plate. An indentation is provided in the end region, preceding the end of the optical fiber, and a separate spherical lens can be inserted into it. Further alignment indentations are formed in the end region, cooperating with the first alignment indentations and forming receptacle spaces. Separate alignment balls can be inserted into the receptacle spaces and provide for positioning and mutual alignment of the two plates in the XYZ directions. The positioning of the optical fiber in the Z direction (axial direction) and the adjustment and positioning of the lens are not described in further detail and must be carried out separately. The known unit has comparatively many individual parts that must each be manufactured precisely, that involve tolerance and that have to be manipulated individually.
Published European Patent Application 0 117 606 A1, corresponding to U.S. Pat. No. 4,767,172, describes a collector for a light-emitting diode row in which each light-emitting diode is assigned a central lens with a concentric parabolic mirror surface, in order to shape light emitted by the light-emitting diode into a parallel beam. The collector is braced through a spacing device on a base plate that carries the individual light-emitting diodes. Therefore the conditions of coupling and beam formation depend not only on the structural height of the light-emitting diodes but also on the tolerances of the seam heights between the light-emitting diodes and the base plate on one hand, and the spacing device and the base plate on the other hand. In the described use of the collector in an electrophotographic recording device, such tolerances are acceptable. However, when light is coupled into an optical fiber, for instance, tolerances that are lower by at least one order of magnitude must be assured.
German Published, Non-Prosecuted Patent Application DE 38 30 119 A1 describes a unit of the type referred to at the outset, in which an optoelectronic component in the form of a laser chip with at least one optically active zone is fixed on a base plate. A lens body has a plane side surface toward the zone and an opposite, convex side surface having a curvature which serves as an aspherical lens. The region between the curvature and the plane side surface necessarily dictates a considerable spacing between the laser and the convex side surface acting as a lens, and that spacing is disadvantageous to the coupling efficiency. Moreover, a material that serves to prevent reflections has to be disposed between the plane side surface and the laser. The laser mirror surface can become stressed and damaged from contact with that material, particularly when there are frequent temperature change cycles.